Syntheses of dibenzo-18-crown-6 lariat isomers and their complexation with lanthanoid nitrates

Two constitutional isomers of dibenzo-18-crown-6 derivatives (6 and 7) were synthesised and their binding behaviours towards trivalent lanthanoid cations (La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+ and Tb3+) were investigated. Both isomers expressed better binding affinities towards Sm3+ and Tb3+ than a group of other lanthanoids, as measured by the ligand-to-metal charge-transfer (LMCT) band intensity at ca. 425nm using UV-vis spectroscopic method. Additionally, the trans isomer 7 was shown to have a higher binding ability than the cis isomer 6 towards Tb3+. [image omitted].